我希望有人可以帮助我解决以下问题，这可能非常基础，但我仍在学习 MVC 3.0（以及一般的编码）。
我得到的值不能为空。参数名称：尝试根据状态 DropDownList 中的值将数据加载到我的城市 DropDownList 时，我的控制器中出现字符串错误。
我希望我只是缺少一些基本的东西。JsonResult getCity调用中的int id = int.Parse(state_id)行引发错误。
这是我的控制器：
public ActionResult Create()
{
ViewBag.sessionName = HttpContext.Session["SPCompanyName"].ToString();
var compID = HttpContext.Session["SPCompanyAccountID"].ToString();
ViewBag.companyID = compID;
List<SelectListItem> list = new List<SelectListItem>();
list.Add(new SelectListItem { Text = "Select State", Value = "Default State" });
var states = (from c in simpleDB.simpleState select c).ToArray();
for (int i = 0; i < states.Length; i++)
{
list.Add(new SelectListItem { Text = states[i].stateFull, Value = states[i].Id.ToString() });
}
ViewData["states"] = list;//data for DropdownList State
List<SelectListItem> list1 = new List<SelectListItem>();
list1.Add(new SelectListItem { Text = "Select City", Value = "Default City" });
ViewData["cities"] = list1;//data for Dropdownlist City
return View();
}
[AcceptVerbs(HttpVerbs.Get)]
public JsonResult getCity(string state_id)
{
int id = int.Parse(state_id);
var myData = (from m in simpleDB.simpleCity where m.simpleStateId == id select new { text = m.cityFull, value = m.Id });
return this.Json(myData, JsonRequestBehavior.AllowGet);
}
这是我的视图的完整代码：
@using (Html.BeginForm(FormMethod.Post))
{
<script src="@Url.Content("~/Scripts/jquery-1.5.1.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/modernizr-1.7.min.js")" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function () {
$('#StateId').change(function () {
var state_id = $(this).val(); //get State ID when select value change
$.getJSON("/SPServiceLocation/getCity/" + state_id, {},
function (myData) {
var options = '';
for (var i = 0; i < myData.length; i++) {
options += '<option value="' + myData[i].value + '">' + myData[i].text + '</option>';
}
$("#CityId").html();
$("#CityId").html(options);
});
});
});
</script>
@Html.ValidationSummary(true)
<fieldset>
<legend>Step 4: Service Areas</legend>
@Html.HiddenFor(model => model.SPCompanyAccountID, new { @Value = ViewBag.companyID })
<div class="editor-label">
@Html.LabelFor(model => model.state)
</div>
<div class="editor-field">
@Html.DropDownList("state", (IEnumerable<SelectListItem>)ViewData["states"], new { id = "StateId", @class = "chzn-select" })
@Html.ValidationMessageFor(model => model.state)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.city)
</div>
<div class="editor-field" id="SP_SelectCity">
@Html.DropDownList("city", (IEnumerable<SelectListItem>)ViewData["cities"], new { id = "CityId", @class = "chzn-select" })
@Html.ValidationMessageFor(model => model.city)
</div>
<p>
<input type="submit" value="Submit" />
</p>
</fieldset>
我已经查看了这个控制器和视图代码几个小时了，只是不知道问题可能是什么。谢谢您的帮助。